Train ride and walk tour in Postojna Cave

Postojna Cave (Slovene: Postojnska jama; German: Adelsberger Grotte; Italian: Grotte di Postumia) is a 24,120 m (79,130 ft) long karst cave system near Postojna, southwestern Slovenia. It is the second-longest cave system in the country (following the Migovec System) as well as one of its top tourism sites. The caves were created by the Pivka River.
Postojna Cave was carved by the Pivka River over millions of years.[14] There are stalagmites, stalactites, and formations called curtains or draperies that look like folded curtains.
The cave system is 24.12 kilometers (14.99 mi) long[15] and is made up of four caves interconnected through the same underground river. However, according to speleology rules, the passages and siphons connecting the caves must be walked or swum through by man for them to be considered one whole. Connecting two of the main cave systems will make this the longest cave system in Slovenia and one of the longest in all of Europe. There remain 400 meters (1,300 ft) between the two caves, which would make the cave system between 31,000 meters (102,000 ft) and 35,000 meters (115,000 ft) long.
The caves are also home to the endemic olm,[16] the largest troglodytic amphibian in the world. The tour through the caves includes an aquarium with some olms in it. On January 30, 2016, a female olm at the cave began to lay over 50 eggs. This rare event led to global news about Postojna Cave and the olm.[17][18] From the end of May to mid-July 2016, twenty-two baby olms successfully hatched.(WIKIPEDIA en.wikipedia.o...)